The present invention is directed to distance determination via a sensor, such as vehicle occupant position sensing within an actuatable occupant protection system, and is particularly directed to control of a rate of the sensor.
Occupant protection systems for use in vehicles are known in the art. One type of protection system includes an actuatable inflatable restraint module, which has an inflatable restraint that is commonly referred to as an air bag. The module is actuated and the air bag is inflated within a vehicle passenger compartment upon the occurrence of a condition for which a vehicle occupant is to be protected. For example, a sensor senses a vehicle condition indicative of a vehicle crash and, in response thereto, the air bag module is actuated.
Occupant protection systems commonly have one or more adjustable aspects, and in order to enhance performance of the protection system, the adjustable aspect(s) are adjusted. In the air bag art, an air bag module that has an adjustable aspect is commonly referred to as a xe2x80x9csmart restraint.xe2x80x9d Examples of adjustable aspects for air bag modules include the deployment dynamic profile of the air bag. Specifically, the inflation timing, the inflation pressure, the rate of inflation, and the positioning of the inflated air bag are all adjustable aspects. Also, suppression of air bag deployment entirely is an adjustable aspect. Adjustment of the air bag module is often responsive to a sensed occupant condition.
In certain circumstances, even if the predetermined deployment vehicle crash condition occurs, it may be preferable to refrain from actuating the air bag module (i.e., deployment is suppressed and the air bag is not inflated). Specifically, if the occupant associated with the air bag module is located in a position such that air bag module actuation will not enhance protection of the occupant, actuation does not occur.
An occupant who is very near an air bag module is referred to as being within an occupant out-of-position (OOP) zone. Deploying an air bag for an occupant who is within the OOP zone will not enhance protection of the occupant. Similarly, when an occupant is near, but not within, the OOP zone, it may be preferable to provide a reduced inflation pressure to the air bag. Often, an occupant is displaced from an initial location that is away from the occupant OOP zone to a location within or near the occupant OOP zone as a result of pre-crash braking or deceleration of the vehicle that occurs just prior to the occurrence of a vehicle crash.
Pertinent occupant condition(s) are sensed and the information regarding the sensed condition(s) is processed in order to control adjustment. Protection systems, such as air bag systems, have sensor(s) for sensing the occupant condition(s). Within air bag systems, ranging sensors are typically used to provide distance information that is utilized to determine if an occupant is within or near an occupant OOP zone.
As an example of a ranging sensor, an ultrasound sensor emits a signal pulse or xe2x80x9cpingxe2x80x9d that is directed at a vehicle occupant location, the pulse is reflected back to the sensor as an echo and is detected. A time duration between emission and reception is commonly referred to as a time-of-flight and is indicative of a distance between the sensor and the occupant. At typical air temperatures, an ultrasonic signal travels at approximately 13.5 inches per millisecond. Thus, one millisecond expires for each 6.75 inches that the occupant is located away from the ultrasound sensor. In one type of vehicle application the ultrasonic signals (pings) are output at 10 millisecond intervals (i.e., at a rate of one ping per 10 milliseconds). This rate allows the sensor to xe2x80x9cbouncexe2x80x9d signals off of an occupant or another object (e.g., a seat back) up to a distance of approximately 67.5 inches from the sensor.
In some circumstances, it may be desirable to determine occupant position (e.g., distance to occupant) more frequently. Such a situation may occur for an occupant who is being displaced forward due to pre-crash vehicle braking or deceleration.
In accordance with one aspect, the present invention provides an apparatus for determining distance to an object. Sensor means of the apparatus senses distance to the object at a sensor rate. Variation means of the apparatus varies the sensor rate as a function of the sensed distance.
In accordance with another aspect, the present invention provides an apparatus that includes means for emitting signals at a rate toward an object. The object reflects the signals. Means receives reflected signals from the object. Means determines a time between emission of a signal and reception of an associated reflected signal. Means determines a distance to the object using the determined time. Means changes the rate of signal emission in response to each change in determined distance.
In accordance with another aspect, the present invention provides an apparatus that includes means for emitting signals at a rate toward an object. The object reflects the signals. Means receives reflected signals from the object. Means determines a time between emission of a signal and reception of an associated reflected signal. Means determines a distance to the object using the determined time. Means continuously changes the rate of signal emission from the means for emitting in response to the determined distance.
In accordance with yet another aspect, the present invention provides an occupant protection system for a vehicle. The system includes an actuatable occupant protection device. Sensor means senses distance to a vehicle occupant at a sensor rate. Determination means makes determinations regarding control of the protection device using the sensed distance. Variation means varies the sensor rate inversely proportional to the sensed distance.
In accordance with yet another aspect, the present invention provides a method for determining distance to an object. Distance to the object is sensed at a sensor rate. The sensor rate is varied as a function of the sensed distance.
In accordance with yet another aspect, the present invention provides a method for controlling an occupant protection device in an occupant protection system for a vehicle. A distance to a vehicle occupant is sensed at a sensor rate. Determinations regarding control of the protection device are made using the sensed distance. The sensor rate is varied inversely proportional to the sensed distance.